Integrated adaptive antenna of a multibeam antenna

ABSTRACT

A multibeam antenna having a plurality of radiators arranged in a form of a dipole field and configured to generate a plurality of lobes, a main antenna including a first set of the plurality of radiators, and an acillary antenna including a second set of the plurality of radiators and configured to suppress disturbances received by the main antenna, wherein each radiator of the second set of radiators makes no significant contribution to lobe generation in the main antenna and whose omission has no effect on the output and directionality of the main antenna.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an antenna arrangement with a plurality ofradiators arranged in the form of a dipole field.

2. Discussion of the Background

An antenna, as is known from EP-A-0 098 339, is configured as aphased-array radar antenna by way of which a main lobe is generated in achronological sequence, and in which context the generated main lobeshave differing directions, in order to irradiate a section of sky. Inthis arrangement, where a dipole field generated by a large number ofmainly horizontal dipole lines arranged one under the other, not alldipoles are connected for configuration of an overall antenna, butrather some adjacent dipoles are combined to form ancillary antennasarranged within the aperture of the main antenna, by which interferencesare suppressed, which are mainly received from the main antenna becauseof subsidiary lobes which cannot be avoided.

SUMMARY OF THE INVENTION

The invention is based on the objective of creating an antennaarrangement including a plurality of radiators which are arranged in theform of a dipole field, for generation of a plurality of lobes in a mainantenna, in which context some of the main radiators of the dipole fieldconstitute an ancillary antenna for suppression of disturbances receivedby the main antenna, which can be employed as a multibeam antenna(multi-lobe antenna) in which context the capacity of a multibeamantenna includes its ability to generate simultaneously in a veryprecise manner, a large number of main lobes (hereafter simplified to“lobes”).

This objective is achieved by a multibeam antenna (multi lobe antenna)configured to simultaneously generate a plurality of main lobes, whereinradiator components in the resultant dipole field, which make nosignificant contribution to the generation of the lobes, are included inthe ancillary antenna and are fed accordingly.

An advantage of the invention resides in the fact that the ancillaryantenna does not increase the size of the overall antenna arrangement.

A further advantage of the invention resides in the fact that becauseneither the topmost nor the bottom lines of the main antenna are usedfor the ancillary antenna radiators (which is also not the case in priorart), the aperture of the main antenna is largely unchanged. By suitablecalculation of the power distribution to individual radiators, forexample dipoles, the antenna can be selected from a wide variety ofpossible power distributions, in which context, for example, two linesof radiators which have spacing from the upper/lower edge of the antennaarrangement for the main antenna, are only fed with such low levels ofcurrent (or, on receive mode, for combination to produce a total signal,only such low levels of current are contributed), that the omission ofthese radiators will exert no practical affect on the output anddirectionality of the antenna. These radiators which thus provide nonoticeable contribution to generation of the lobes for the main antennaand are not needed for the main antenna, are used as ancillary antennason receive mode. The invention does not exclude co-utilization ofradiators of the ancillary antenna in transmit mode for transmission,but such that they support the configuration of the lobes of the mainantenna.

It may also be advantageous to implement calculation of the powerdistribution of individual radiators of the main antenna such that onlyan individual line produces no significant contribution towards theconfiguration of lobes, and thus only one individual line of radiatorswill be used as the ancillary antenna in receive mode.

It is not necessary for a complete line (or several complete lines) ofradiators to configure the ancillary antenna, nor is it necessary ifdesign considerations, particularly considerations of supply to theindividual radiators should possibly make it advantageous for at leastseveral radiators from a single line to be employed for the mainantenna.

In accordance with the invention, then, it is possible to set up anantenna system in which, if—for example from an elevation angle of 3°above the plane of the horizon and below it (from this area, onlydisturbance signals are anticipated)—the reception of signals which havebeen received from the main antenna should be suppressed by theancillary antenna for each individual one of the lobes operatedsimultaneously in the radiation curve of the main antenna, then at leastone lobe of the ancillary antenna, whose elevation is for exampleapproximately 3°, can simultaneously be generated.

In respect of the main lobes, it should also be mentioned that these arein general arranged according to several lines and columns (usually notin a precise rectilinear arangement in relation to each other), in whichcontext the center of the main lobe of each individual lobe is at thecrossover of the lines and columns.

In the case of form of embodiments in accordance with the invention, itis envisaged, for supply to the main antenna and to the ancillaryantenna, that there should be a joint feed network which should ideallybe constructed of Butler matrixes and Blass matrixes. The system is madeup such that the transmit/receive arrangement of the antenna system isconnected to input from the Blass matrixes, whose outputs are connectedto inputs for the Butler matrixes whose outputs are in turn eachconnected to an individual radiator. Under this arrangement with acommon feed matrix, there is also the option in certain operating cases,for examples in transmit mode, of using radiators of the ancillaryantenna (or additional antenna) for purposes of transmission if desired.

In the example shown, the Blass matrixes bring about “pivot” (this isthe change in direction in relation to the direction runningperpendicular to the plane of the antenna aperture) in elevation, whilstthe Butler matrixes bring about pivot in azimuth.

Under the other form of embodiment of the invention, on the other hand,it is envisaged that the main antenna and the additional antenna,although this is topographically arranged within the main antenna,should be fed from entirely separate feed networks.

BRIEF DESCRIPTION OF THE DRAWINGS

As an alternative for using one line (in the horizontal plane) ofradiators in the antenna system for purposes of the ancillary antenna,it would alternatively be possible, depending on the applications, toenvisage one column.

Further characteristics and advantages of the invention can be seen fromthe description of examples of embodiment for the invention on the basisof the drawing which illustrates the main details of the invention, andfrom the claims. Individual characteristics can be embodied individuallyand on their own or in groups of several units in any combination for agiven form of embodiment of the invention.

There are illustrated in:

FIG. 1: a plan view of the dipole field in a multibeam antenna with 16×8dipoles,

FIG. 2: Overview of an antenna system using the dippole filed as perFIG. 1 in accordance with an initial example of embodiment with separatefeed to the additional antenna,

FIG. 3: An arrangement corresponding to FIG. 2 with a standardised feedarrangement for the main antenna and ancillary antenna or additionalantenna, and,

FIG. 4: The structure of feed network 50 from FIG. 3 in respect of Blassmatrixes and Butler matrixes.

DESCRIPTION OF THE EMBODIMENTS

In the example, the dipole field consists of a planar arrangement of 16lines and 8 columns of dipoles, thus 16×8 dipoles. The dipoles arevertical-polarised and aligned parallel to the plane of antenna aperture1. In operation, the arrangement as per FIG. 1 is not vertical but isinclined at an angle of 45° in relation to the vertical plane, such thatthe longitudinal axis of individual dipoles 3 does not run verticallybut inclines at the above-mentioned angle of 45° in relation to thevertical.

The dipoles have an integral of 0.45 lambda rectangular to the dipoleaxis (“azimuth”) and of 0.55 lambda in the dipole axis (“elevation”).

In the form of embodiment as per FIG. 2, it is assumed that the powerdistribution for individual dipoles 3 is designed such that, startingfrom below, the 3^(rd) and 14^(th) line of a given set of 8 dipoles forconfiguration of the main antenna lobes do not make any significantcontribution in receive mode and in the ideal instance only a negligiblecontribution. These 3^(rd) and 14^(th) lines of the dipoles are employedas ancillary antennae. This fact is not evident from FIG. 2, but here,the ancillary antenna is represented purely as arrangement 5 of 2×8dipoles whilst the main antenna represents an arrangement 6 of 14×8dipoles.

Antenna aperture 1 or dipole field 1 of FIG. 2 receives, i.e. is fed,via two separate feed networks 10 of 12, where feed network 10 feeds theancillary antenna and feed network 12 feeds the main antenna. Here, asis the general practice, the expression “feed network” is employed,although in a receive mode, naturally, there is no feed to the antennaebut a convergence (vectorial addition) of signals supplied by theantennae.

Feed network 10 exhibits two Butler matrixes 14, each of which feeds oneof the above-mentioned lines of 8 dipoles of the 2 dipole line employedfor the ancillary antenna, and 6 vertical feed networks 15 which feedthe Butler matrixes. The connection of the vertical feed network 15shown at the bottom in FIG. 2, to which the signals originating from theadditional antenna arrive in receive mode, are designated by referencemarks A1 to A20. In the drawing, the further connection of connection A1is indicated. Each vertical feed network 15 is configured by a phaseshifter and a divider 1:2 or 1:4 which connects the phase shifter to the2 or 4 connections of the respective vertical feed network to the one inthe lower section of FIG. 2.

Feed network 12 for the main antenna with 14×8 dipoles includes 14Butler matrixes (one Butler matrix for each of the 14 dipole lines ofthe main antenna) and 6 Blass matrixes. These are not illustratedindividually but are included in the installation (feed network)designated by reference mark 12. Feed network 12 exhibits 20 connectionsH1 to H20. Here too, the further circuitry is illustrated exclusivelyfor output H1. From the feed network 12, the 112 feed lines lead to112(=14×8) dipoles of the main antenna.

In respect of feed network 10, the 20 connections A1 to A20 provide thereception signals for the 20 ancillary lobes of the ancillary antenna.Each ancillary lobe is allocated specifically to one of the 20 mainlobes of the main antenna, whose reception signals are available atconnections H1 to H20.

Connection A1 of feed network 10 leads to a connection of a digitallyadjustable phase shifter 30, whose output is connected to the input ofan attenuator 32 which has digital adjustment in respect of its gain ordamping, whose output leads to an input of a summing circuit 34, whichexhibits a further input which is connected to connection H1 of feednetwork 12. The output from summing circuit 34 leads to furtherinstallation in the radar system which analyses the received signal. Aproportion of the signal originating from the outputs of summing circuit34 is fed via a coupling installation 36, in the example a relaycoupler, an amplifier 37 and subsequently a demodulator 38, and finallyvia an analogue/digital converter 39, to a digital adaptive processor40. This exhibits a digital processor which actuates phase shifter 30and attenuator 32 via control lines such that the signal fed toprocessor 40 from digital/analogue converter 39 is minimised. Once thathas been achieved, then optimum suppression of the interference signalfrom the first lobe is achieved.

For each individual one of the other connections A2 to A20 of feednetwork 10 and H2 to H20 of feed network 12, the above-describedcircuit, including the phase shifter, the attenuator, the summingcircuit, and the installations subordinate to the same are alsoenvisaged such that for all 20 lobes simultaneously, and thus veryrapidly, adaptive regulation can be performed by way of the processor 40allocated in each case. If it is feasible in the context of the speed ofcalculation of processor 40 and the required operating speed of theradar antenna, then it is also possible to envisage purely a singleprocessor 40 which consecutively processes all 20 output signals of feednetwork 10 and of feed network 12.

The example of embodiment as per FIG. 3 does not differ in respect ofits dipole field and in the arrangement of the 3^(rd) and 14^(th) lineof the dipole to the ancillary antenna and of the other dipole to themain antenna in relation to the dipole field of FIG. 2. However, here,there are not different feed networks for the ancillary antenna on theone hand and the main antenna on the other, but a standardised feednetwork 50 consisting of 16 Butler matrixes 52 and 6 Blass matrixes 54,see FIG. 4. Feed network 50 as illustrated exhibits 20 outputs H1 to H20for the main lobes of the main antenna and 20 outputs A1 to A20 for theancillary lobes of the ancillary antenna. Outputs H1 to H20 of the mainantenna are, as in FIG. 2, envisaged in the right-hand section of theFigure, whilst outputs A1 to A20 of the ancillary antenna are providedwith installations designated Z1 to Z6, relating to l:n splitters(namely 1:2-splitter and 1:4-splitter). The remaining circuitryconcerning items 30, 32, 34, 36, 37, 38, 39 and 40 is consistent withFIG. 2.

In the examples shown, the multibeam antenna together with its mainantenna section in the cases of FIGS. 2 and 3 simultaneously generatesfour lines with six columns of main lobes, in which context, however,some columns are not equipped with four main lobes, but that overallthere are only 20 main lobes. The ancillary antenna, in a range of 3°above the plane of the horizon, generates 20 main lobes, each of whichis allocated to a main lobe of the main antenna.

As illustrated in FIG. 4, connections Z1 to Z6 represent an additionaloutput of the total of 6 Blass matrixes 54. Furthermore, these exhibitthe 20 connections H1 to H20 which are used for feed to the mainantenna, specifically for generation of one of lobes 1 to 20. The upperconnections in FIG. 4 for the Butler matrixes 52 are each connected toone of the radiators (dipole) of antenna 1. Each upper connection inFIG. 4 for the first Blass matrix (Blass 1) is connected to the firstlower connection of the individual Butler matrixes. The furtherconnection can be seen in FIG. 4, in which context not all individualconnections are illustrated.

In the selection of radiators for the ancillary antenna, it shouldbetaken into account that the phased centers of the main antenna and ofthe ancillary antenna are identical or are at least very close to eachother. This is advantageous because this situation also means that if adisturbance source to be suppressed is exhibiting rapid movement, forexample as in an aircraft, the relative phase between the receptionsignals for the main antenna and those for the ancillary antenna variesonly slightly. In the above-described examples of embodiment, therequired identically of phased centers is present because of thesymmetrical arrangement of the ancillary antenna dipoles in relation tothe overall dipole field.

In FIG. 1, the following dimensions are envisaged in the example given:length a of antenna aperture=5.90 m, width b=2.38 m, dipole intervalcenter—center in plane a=0.366 m, d=0.3 m.

What is claimed is:
 1. A multibeam antenna comprising: a plurality ofradiators arranged in a form of a dipole field and configured togenerate a plurality of lobes; a main antenna including a first set ofsaid plurality of radiators; and an ancillary antenna including a secondset of said plurality of radiators and configured to suppressdisturbances received by the main antenna, wherein each radiator of saidsecond set makes no significant contribution to lobe generation in themain antenna and whose omission has no effect on an output anddirectionality of the main antenna.
 2. The multibeam antenna accordingto claim 1, wherein the main antenna is configured such that specificradiator elements, not topmost nor bottom line radiator elements, have apower allocation which make no significant contribution to lobegeneration in the main antenna.
 3. The multibeam antenna according toclaim 1 or 2, further comprising: two separate feed networks, one feednetwork configured to feed said first set of said plurality of radiatorsof the main antenna, and another feed network configured to feed saidsecond set of said plurality of radiators of the ancillary antenna. 4.The multibeam antenna according to claim 3, wherein at least one of thetwo feed networks includes at least one of a Butler matrix and Blassmatrix.
 5. The multibeam antenna according to claim 3, wherein outputsof the main antenna and the ancillary antenna are combined for adaptivecompensation of interference signals.
 6. The multibeam antenna accordingto claim 1 or 2, further comprising: a feed network configured to feedsaid first set of said plurality of radiators of the main antenna and tofeed said second set of said plurality of radiators of the ancillaryantenna.
 7. The multibeam antenna according to claim 6, wherein the feednetwork includes at least one of a Butler matrix and Blass matrix. 8.The multibeam antenna according to claim 6, wherein outputs of the mainantenna and the ancillary antenna are combined for adaptive compensationof interference signals.
 9. The multibeam antenna according to claim 1or 2, wherein phase centers of the main antenna and the ancillaryantenna are closely adjacent to each other.